This addon is Unsupported as of 2015 until further notice. I have not enough time or interest in vbulletin to keep this alive.

This addon provides a framework for future extensions which make use of the Steam API.
It helps to determine the SteamID of an user. Unless older methods of inserting the steam
id into a user field, the addon lets the user authenticate with Steam OpenID, therefore
you can trust 100%, that this particular user is the same user as the Steam-ID provided.

Users can link their Steam ID to their forum account or they can create a new account
using details pulled from their Steam Profile.
Like the Facebook connect plugin, it allows users to quickly set up a forum account without
having to define a password or an email address. This option can be disabled in the AdminCP,
however it is encouraged to allow users to use this quick-register feature, since they
already authenticated themselves through steam, so any additional password or email
authentication is just unnecessary.

If the user decides to un-link his forum account with his steam-profile, he has to set up
a password and email first, so the forum account remains usable after this.

At the moment, the addon is in its second RC state, which means that the current versions contain mostly bugfixes and are candidates for a full release.
Until now, the product worked without major problems in productive environments. Although it is stable as is, the author doesn't provide any guarantee.
Due to the nature of the addon and how vBulletin manages 3rd party code inclusion, additional
login and register methods have been provided by the plugin. It is discouraged to use the
plugin on high profile communities in this early development state.

If you have any further questions, feel free to post in this thread.

F.A.Q. / General Issues / Error Messages

"There has been a problem with the OpenID libary: No OpenID Server found at http://steamcommunity.com/openid"
- Additionally, a 503 HTTP error is thrown. Simple solution: Wait. Steam Community servers are overloaded/down right now, there's nothing you can do about it

Do NOT uninstall the mod if you want to keep the linked users records. Upgrading means uploading the new product xml file for the new version and choose "overwrite" in the upload dialog.
The Installer will handle the update process by its own. Uninstalling the product will erase all the table fields which contain the steam link data.

I had an issue where it eventually after about a month stopped retrieving profile data for no reason at all but still worked, possibly because of a semi-domain change, but otherwise works if your settings are right.

FIXED: I will leave this here for anyone having similar issues in the future. The issue for me was the API key. It may be worth resetting the key if you encounter similar issues which do not give error logs.